JP2001261751A - Method for producing graft copolymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a graft polymer latex without causing the lowering of productivity in the method for producing the polymer latex by carrying out the graft polymerization of a graft polymerizable monomer with a rubber latex. SOLUTION: This graft polymer latex is produced without causing the lowering of the productivity by adding an electrolyte, suppressing the foaming of the latex and thereby removing the unreacted monomer in a short time when the unreacted monomer is removed from the rubber latex before carrying out the graft polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ABS resin or an MB resin.
The present invention relates to a method for producing a graft copolymer latex by graft-polymerizing a monomer capable of graft polymerization to a rubber latex, which relates to an emulsion polymerization method of an S resin or the like,
More particularly, the present invention relates to a method for producing a latex of a graft copolymer by removing unreacted monomers in a rubber latex before graft polymerization without lowering quality and lowering productivity.

[0002]

2. Description of the Related Art A polymer produced by graft-polymerizing a monomer capable of being graft-polymerized with a latex rubber containing a conjugated diene as a main component is an ABS resin (acrylonitrile-butadiene-styrene), It is known that it is used for various purposes such as MBS resin (methyl methacrylate / butadiene / styrene) and high impact polystyrene, and is used mainly for the purpose of improving impact resistance.

On the other hand, in the method for producing a polymer by such a method, if graft polymerization is carried out in a state where unreacted monomers remain in the rubber latex, the impact resistance of the produced product is lowered. In order to reduce the properties of the graft copolymer, it is necessary to remove unreacted monomers remaining in the rubber latex before performing the graft polymerization.

As a method for removing unreacted monomers in a rubber latex, a method of performing steam distillation as described in JP-A-55-41829 is often used. However, in this method, deterioration of the polymer and generation of a coagulated material due to heat occur, which causes a decrease in product quality and a decrease in production efficiency. In addition, the use of water vapor causes a decrease in the solid content concentration of the rubber latex due to the condensed water, resulting in a decrease in productivity.

As other methods, a method of removing unreacted monomers under reduced pressure and a method of bubbling an inert gas as described in JP-A-2-199103 are known. . However, in these methods, foaming occurs when applied to a foamable latex,
Reduction of product yield due to coagulation, reduction of heat transfer efficiency during graft polymerization due to adhesion of coagulation to the polymerization machine wall, pollution of equipment and environment due to latex being discharged through decompression device The problem occurs. In particular, when a rubber latex having a high solid content is produced in order to improve productivity, the above problem becomes more serious with an increase in the viscosity of the rubber latex.

In order to address these problems, it is necessary to reduce foaming of the latex when removing unreacted monomers, and as a specific method, a method of suppressing the removal amount of unreacted monomers per unit time is low. And use of an antifoaming agent, but in the former method, it takes time to reduce the concentration of the unreacted monomer, so that there is a problem that the productivity decreases, and in the latter method, However, there is a problem that types of rubber latex and types of defoamers that can be applied are limited.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention relates to a method for producing a graft copolymer latex by graft-polymerizing a monomer capable of being graft-polymerized to a rubber latex. An object of the present invention is to provide a method for producing a graft polymer latex without causing a decrease in quality and productivity.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above-mentioned problems, it has been found that adding an electrolyte before removing unreacted monomers from the rubber latex allows the rubber latex to be dissolved. We found that it was possible to suppress the foaming property to a low level, and even with a method of removing unreacted monomers under reduced pressure and a method of bubbling an inert gas, unreacted monomers were suppressed while suppressing foaming of the rubber latex. It has been found that it is possible to remove it. According to this method, the amount of unreacted monomer removed per time can be increased as compared with the conventional method, which is extremely effective in improving productivity.

As a result of further studies by the present inventors, the electrolyte used in the above method is an organic acid containing a carboxyl group and having 6 or less carbon atoms or a salt thereof, or an inorganic sodium salt or an inorganic potassium salt. Alone or a mixture of two or more of them has been found to be more effective.

As a result of further studies by the present inventors, they have found that it is more effective to use a neutral salt as the electrolyte.

That is, the present invention relates to a method for producing a graft copolymer latex in which one or more monomers capable of graft polymerization with this rubber are graft-polymerized onto a latex-like conjugated diene rubber. A method for producing a graft copolymer latex, comprising adding an electrolyte to the latex, removing unreacted monomers in the rubber latex in the presence of the electrolyte, and then performing graft polymerization (claim 1); 2. The graft copolymer according to claim 1, wherein the electrolyte is an organic acid containing a carboxyl group and having 6 or less carbon atoms or a salt thereof, or an inorganic sodium salt or an inorganic potassium salt alone or as a mixture of two or more. 2. The method for producing a polymer latex (Claim 2), and the graft copolymer latek according to claim 1, wherein the electrolyte is a neutral salt. It relates to a process for producing (claim 3).

[0012]

DETAILED DESCRIPTION OF THE INVENTION The polymer latex according to the method of the present invention emulsifies a conjugated diene monomer or a monomer containing a conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith. It is a graft copolymer latex obtained by graft copolymerizing the following graft copolymerizable monomer with a conjugated diene rubber latex obtained by polymerization.

Here, the conjugated diene monomer includes 1, 1
Examples thereof include 3-butadiene, isoprene, and chloroprene, and 1,3-butadiene is particularly preferable.

Examples of the ethylenically unsaturated monomer copolymerizable with the conjugated diene-based monomer include various vinyl compounds and olefin-based compounds. Particularly, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, etc. Acrylic esters, for example, methyl acrylate, ethyl acrylate, etc., aromatic vinyls; for example, styrene, α-methylstyrene, etc., or their nuclear-substituted derivatives; for example, vinyl toluene, chlorostyrene, etc., vinyl cyanide; for example, acrylonitrile Is appropriate. These are used alone or in a mixture of two or more.

Examples of the graft-polymerizable monomer include an aromatic vinyl compound; for example, styrene, α-methylstyrene, or an acrylate; for example, methyl acrylate, ethyl acrylate, or a methacrylate; Methyl methacrylate,
Ethyl methacrylate, etc., or acrylonitrile,
Acrylic acid, methacrylic acid and the like can be mentioned, and these can be used alone or in combination of two or more.

The rubber latex is a monomer that is 100 parts by weight of a conjugated diene monomer or a mixture containing a conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith, 100 parts by weight of a monomer in which the ratio of the conjugated diene monomer to all the monomers is 70% by weight or more,
Preferably 60 to 200 parts by weight of water, more preferably 70
It is obtained by emulsion polymerization in the presence of １５０150 parts by weight. The reaction temperature is 30 ° C. or higher, preferably 35 ° C.
C. to 80C, more preferably 40C to 60C.

Here, the ratio of the conjugated diene monomer to all the monomers including the conjugated diene monomer and the ethylenically unsaturated monomer copolymerizable therewith is preferably 70% by weight or more, more preferably 70% by weight. If it is less than 10%, the properties of the polymer as a rubber are too small to obtain toughness.

Examples of the polymerization initiator used in the present invention include water-soluble persulfuric acid such as potassium persulfate, sodium persulfate and ammonium persulfate, and peroxides such as hydrogen peroxide, cumene hydroperoxide and paramenthane hydroperoxide. A redox initiator as one component can be used.

The amount of the emulsifier used is preferably 1 to 4 parts by weight based on 100 parts by weight of the total monomers. An emulsifier may be added during polymerization in order to keep the particles from fusing with each other or generating repellent due to lack of the emulsifier on the surface of the particles. The emulsifiers used are those used in ordinary rubber polymerization, such as fatty acid soaps such as sodium oleate, or resin acid soaps such as disproportionated potassium rosinate, sodium lauryl sulfate, dodecylbenzene sulfonic acid. An example is soda.

The use of a chain transfer agent such as mercaptan or a cross-linking agent such as allyl methacrylate is not limited at all.

In the present invention, an organic acid, a metal salt thereof, an inorganic alkali metal salt or the like can be used as an electrolyte to be added to the rubber latex after the polymerization of the rubber latex and before removing unreacted monomers. . In particular, formic acid, acetic acid, propionic acid, oxalic acid, succinic acid, malic acid, citric acid and the like, an organic acid having a carboxyl group of 6 or less or a salt thereof, or an inorganic sodium or potassium salt alone or A mixture of two or more types can more effectively suppress foaming of the rubber latex.

Also, sodium chloride, sodium sulfate,
It is preferable to use a neutral salt such as sodium nitrate or potassium sulfate because foaming of the rubber latex can be more effectively suppressed.

The above-mentioned electrolyte is preferably added to the rubber latex in the form of an aqueous solution of 1 to 20% by weight.

The decrease in the foaming property of the rubber latex due to the addition of the electrolyte is effected by the effect of the electrolyte to cancel the foaming property of the rubber latex by the emulsifier in the rubber latex, and by the formation of fine aggregates of the rubber latex by the electrolyte. This is due to both the effect of reducing the viscosity of the polymer. In the case where the aggregation of the rubber latex causes a decrease in the quality of the product, it is possible to sufficiently reduce the foaming property of the rubber latex by adding an amount of an electrolyte that does not agglomerate the rubber latex. If it is possible to agglomerate the rubber latex, foaming of the rubber latex can be reduced more effectively by adding an electrolyte to such an extent that a fine aggregate of the rubber latex is formed.

In the above, when it is possible to agglomerate the rubber latex, the particle size of the rubber latex aggregate obtained by adding an electrolyte is preferably not larger than 0.5 μm. When the particle size of the rubber latex aggregate exceeds 0.5 μm, the graft ratio of the polymer after graft polymerization is reduced, and the quality of the product tends to be impaired.

The amount of the electrolyte to be added is preferably 10 to 100 parts by weight of the emulsifier contained in the rubber latex.
Addition of from 95 to 95 parts by weight, more preferably from 60 to 95 parts by weight, is desirable from the viewpoint of suppressing foaming of the rubber latex.

The method of removing the unreacted monomer is not particularly limited, but a method of removing the unreacted monomer under reduced pressure, a method of bubbling an inert gas, or the like is used. The present invention is particularly effective in a method not using it.

The latex obtained after the graft polymerization is
It can be treated by a standard method used in a production method of an ABS resin or MBS resin by emulsion polymerization. For example, the polymer latex can be coagulated by a known acid-salt coagulation method; for example, a gas phase coagulation method, a liquid phase coagulation method, etc., and then the mixture of water present after coagulation and the polymer suspended therein is filtered or filtered. It can be separated by a method such as centrifugation. After separation of the mixture of water and polymer suspended therein, the wet polymer can be dried by known methods. Also,
The latex obtained after the graft polymerization can be granulated and dried by a spray dryer.

[0029]

The present invention will be described below with reference to examples.
Note that the present invention is not limited to those described in the examples. In addition, each evaluation item in an Example was measured by the following method. (Amount of unreacted monomer) About 2 g of rubber latex was placed in an Erlenmeyer flask, precisely weighed, and methyl ethyl ketone was added to this.
Add 2 ml to coagulate the latex. Next, 20 ml of tetrahydrofuran is added, 0.02 g of cyclohexane is precisely weighed and injected. After that, the conical flask is stoppered and shaken sufficiently, and the unreacted monomer is extracted with tetrahydrofuran. The tetrahydrofuran phase is collected with a microsyringe, and the amount of unreacted monomer is measured by gas chromatography. The amount of the unreacted monomer in the rubber latex is represented by% by weight based on 100% by weight of the solid content of the rubber latex. (Amount of repellent) After the latex after the graft polymerization is filtered through a 100-mesh wire net, the solid material on the 100-mesh wire net is washed with water, dried and weighed to obtain the amount of repellent. The amount of repellent is expressed as a percentage by weight based on 100% by weight of the total monomers used to prepare the weight fraction of the filtered latex. (Rubber Latex Particle Size) The particle size of the rubber latex is measured by a NICOMP particle size measuring device manufactured by Pacific Scientific Corporation.

The rubber latex used in Examples and Comparative Examples was produced by the following method. (Production method of rubber latex) 1,3-butadiene 100 was placed in a pressure-resistant polymerization machine having an inner volume of 3 L and degassed under vacuum.
2.0 parts by weight of semi-hardened tallow fatty acid potassium, 0.44 parts by weight of tripotassium phosphate, 0.2 parts by weight of n-dodecyl mercaptan, and ferrous sulfate 0.0014 parts by weight
Parts by weight, disodium ethylenediaminetetraacetic acid
0023 parts by weight, 0.2 parts by weight of sodium sulfoxylate / formaldehyde, 77 parts by weight of pure water
The mixture was stirred and heated to 40 ° C. After reaching the predetermined temperature,
The polymerization was started by adding 0.05 parts by weight of paramenthane hydroperoxide. After 13 hours reaction time,
A rubber latex having a solid content of 46.3% by weight, a particle size of 0.080 μm, and an unreacted monomer amount of 2.8% by weight was obtained.

(Example 1) The rubber latex obtained by the above-mentioned method was charged into a glass-made vacuum-resistant container having a content of 3 L, and 0.30 weight of sodium sulfate was added per 100 weight parts of solid content of the rubber latex. Was added.

Next, the temperature of the rubber latex was raised to 60 ° C., and the exhaust capacity was 18
The pressure is reduced by a vacuum pump of L / Hr and the degree of pressure reduction is 150 mmH
g, the distance from the interface between the foam layer and the rubber latex to the upper end of the foam layer when the foam layer accumulated on the rubber latex liquid surface was the largest (hereinafter referred to as foaming). (Referred to as layer height).

When the degree of pressure reduction reaches 150 mmHg, the vacuum pump is stopped, the internal pressure of the polymerization machine is increased to atmospheric pressure with nitrogen, and rubber latex is collected to determine the amount of unreacted monomer and the particle size of rubber latex. It was measured.

Next, per 100 parts by weight of the solid content of the rubber latex, a monomer mixture of 28 parts by weight of methyl methacrylate and 15 parts by weight of styrene, 0.10 part by weight of t-butyl hydroperoxide, 0.1 part by weight of oleic acid. 03
Graft polymerization was performed by continuously adding parts by weight of the mixed solution, and the amount of reticulates of the latex obtained after the graft polymerization was measured. The results are shown in Tables 1 and 2.

Example 2 The same operation as in Example 1 was performed except that the amount of sodium sulfate added to the rubber latex was changed to 0.59 parts by weight per 100 parts by weight of the solid content of the rubber latex. The results are shown in Tables 1 and 2.

Example 3 The same operation as in Example 1 was performed except that the electrolyte added to the rubber latex was changed to 0.60 parts by weight of oxalic acid per 100 parts by weight of the solid content of the rubber latex. The results are shown in Tables 1 and 2.

Example 4 The rubber latex obtained by the above-described method was charged into a glass-made vacuum resistant container having a content of 3 L, and 0.30 wt. Of sodium sulfate was added per 100 wt. Was added.

Next, the rubber latex was heated to 60 ° C., and stirred at a rotation speed of 400 rpm, while adjusting the displacement of a vacuum pump so that the height of the foam layer was maintained at 0.15 m. Was decompressed, and the time required until the degree of decompression reached 150 mmHg was measured.

When the degree of pressure reduction reached 150 mmHg, the vacuum pump was stopped, the internal pressure of the polymerization machine was increased to atmospheric pressure with nitrogen, and rubber latex was collected to determine the amount of unreacted monomer and the rubber latex particle diameter. It was measured. Table 1 shows the results.

Example 5 The same operation as in Example 3 was performed except that the amount of sodium sulfate added to the rubber latex was changed to 0.59 parts by weight per 100 parts by weight of the solid content of the rubber latex. Table 1 shows the results.

(Comparative Example 1) The same operation as in Example 1 was performed except that sodium sulfate was not added. When the inner pressure of the vacuum-resistant container reaches 270 mmHg, the height of the foam layer is 0.3.
3 m, and the foam layer reached the upper end inside the vacuum-resistant container. When the pressure was further reduced, the foam flowed out of the container.
The results are shown in Tables 1 and 2.

Comparative Example 2 The same operation as in Example 3 was performed except that sodium sulfate was not added. Table 1 shows the results.

[0043]

[Table 1]

[0044]

[Table 2] From the results in Table 1, it can be seen that the method of the present invention can remove unreacted monomers in the rubber latex in a shorter time than before, while suppressing foaming of the rubber latex.

From the results shown in Table 2, it can be seen that the method of the present invention can also achieve the same amount of rejects after graft polymerization as in the conventional method.

[0046]

According to the present invention, there is provided a method for producing a polymer latex by graft-polymerizing a monomer capable of being graft-polymerized to a rubber latex, wherein unreacted monomers are removed from the rubber latex in a short time. It is intended to produce a graft polymer latex without lowering the productivity.

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Claims (3)

[Claims] 1. A method for producing a polymer latex in which one or more kinds of monomers capable of graft polymerization with a rubber are graft-polymerized to a latex-like conjugated diene rubber, wherein an electrolyte is added to the rubber latex before the graft polymerization. Removing the unreacted monomers in the rubber latex in the presence of an electrolyte and then performing graft polymerization. 2. The method for producing a graft copolymer latex according to claim 1, wherein the electrolyte is an organic acid containing a carboxyl group and having 6 or less carbon atoms or a salt thereof, or an inorganic sodium salt or an inorganic potassium salt. . 3. The method for producing a graft copolymer latex according to claim 1, wherein the electrolyte is a neutral salt.